This invention relates to an improvement in a rotary direction detecting sensor designed to detect the rotary direction of a steering wheel in order to stop the blinking of a turn indicator light of a vehicle.
In a vehicle nowadays, a switch for blinking a turn indicator light is often mounted in a place other than a steering column such as an instrument panel. In such case, when the steering wheel is returned to its original position after the turn is completed, a rotary direction detecting sensor is required in order to put off the turn indicator light by detecting the rotary direction.
One such rotary direction detecting sensor for serving this purpose is suggested in Japanese Utility Model Reg. Appln. Post-Examination Publication No. 56-172766 (1981).
The rotary direction detecting sensor of this type is shown in FIGS. 1 to 3, which will be now described hereunder with reference to the drawings.
In the drawings, steering wheel 2, steering shaft 2 and fixed member or stationary member 3 fixedly mounted on a steering column side and having a central cylindrical portion 3a, into which the steering shaft 2 is thrusted. A first rotor 4 is rotatably fitted on the central cylindrical portion 3a. The frist rotor 4 is provided with a collar 4b having a projection 4c which is inserted into a bore 1a defined in the steering wheel 1 in such a manner that the first rotor 4 is rotated in accordance with the rotation of the steering wheel 1.
A second rotor 5 having a cylindrical portion 5a and fitted on a cylindrical portion 4a of the first rotor 4 in such a manner as to be rotatable in association with the rotation of the second rotor 5 but being only slidable in the axial direction just the same as the relation between a key and a key groove. A third rotor 6 is rotatable in association with the rotor 5 in the same direction by means of a meshing engagement relative to each other. A semi-fixed member or semi-stationary member 7 is loosely fitted on a step portion 6a of the third rotor 6 and having a projection 7a inserted into a groove 3e of the stationary member 3, the semi-stationary member 7 contacting a projected ring 5d which is biased by a spring 8 stretched between the collar 4b and the second rotor 5.
When the steering wheel is rotated, the second rotor 5 is also rotated because of the mutual relation as mentioned above. Although the semi-stationary member 7 is also inclined to rotate due to the friction force relative to both the projected ring 5d and the step portion 6a of the third rotor, it stops rotating after being rotated for or at a predetermined angle since the projected portion 7a hits the end of the groove 3e.
The stationary member 3 is provided with two contacts 3b, 3c on its right and left portions at equal angles with respect to the groove 3e. The semi-stationary member 7 is provided with a contact 7b which is to be put in alignment with either the contact 3b or contact 3c depending on the rotary direction (when it is rotated for or at a predetermined angle as mentioned above,) while said second rotor 5 is provided with a bifurcated spring contact 5c for contacting said contacts 3b, 3c and the contact 7b.
Consequently, when the semi-stationary member 7 is rotated for or at a predetermined angle due to the rotation of the steering wheel, the spring contact 5c contacts with either of the contacts 3b and 7b, or 3c and 7b depending on its rotary direction so that the circuit is closed therebetween.
However, in this rotary direction detecting sensor, since the semi-stationary member is provided at the inner periphery of the stationary member having fixed contacts and this semi-stationary member and the second rotor 5 are provided with a contact respectively, 2 lanes are required only for contacts. In addition, the aforementioned structures are required. Therefore, the diameter of the sensor becomes very large.
Because of the above mentioned reasons, a rod-type horn contact could not be used. Furthermore, a leaf spring type contact which is now commonly used could not be used, because when employed, a problem is caused involving interference with the column cover.